Problem: If $5a + 8b + 5c = 8$ and $3x + 2y + 2z = 7$, what is $-6x - 4y - 4z + 40a + 64b + 40c$ ?
$= 40a + 64b + 40c - 6x - 4y - 4z$ $= (8) \cdot (5a + 8b + 5c) + (-2) \cdot (3x + 2y + 2z)$ $= (8) \cdot (8) + (-2) \cdot (7)$ $= 64 - 14$ $= 50$